Polyurethane foams having high resilience are typically produced from polyether triol and an isocyanate. The polyether triols typically have a number average molecular weight from 4,500 to 6,000 and an average functionality of from 2.4 to 2.7 hydroxyl groups per molecule. Toluene diisocyanate, diphenyl methane diisocyanate, toluene diisocyanate/diphenyl methane diisocyanate mixtures, and modified toluene diisocyanate or diphenyl methane diisocyanate versions are used to produce foams with broad processing latitude. Isocyanate functionality is typically 2.0, and in most cases not higher than 2.3 isocyanate groups per molecule. The polyether triols form resilient foams when combined with the isocyanates having from 2.0 to 2.3 isocyanate groups per molecule under conditions which promote foaming.
U.S. Pat. No. 4,939,184 described the production of polyurethane foams from polyisobutylene triols and diols which were prepared cationically. The polyisobutylenes are premixed with an isocyanate, namely an isocyanate which is a mixture of meta- and para- isomers of toluene diisocyanate having a functionality of 2.0. Then water was added as a blowing agent to form the polyurethane foam. Foams obtained were of low resilience and were useful in energy absorbing applications.
U.S. patent application Ser. No. 08/494,640, incorporated herein by reference, described a high resilience polyurethane foam produced from a polydiene diol. The foam's resiliency was achieved by adding an aromatic polyisocyanate having a functionality of from 2.5 to 3.0 isocyanate groups per molecule to assure adequate crosslinking. The polydiene diol foams produced showed excellent humid aging properties in comparison to conventional polyurethane foams.
U.S. Pat. No. 5,710,192, incorporated herein by reference, described a high resilience, high tear resistance polyurethane foam produced from a polydiene diol. The foam's resiliency was achieved by selecting an appropriate amount of a aromatic polyisocyanate having a functionality of from 1.8 to 2.5 isocyanate groups per molecule to assure adequate crosslinking. The polydiene diol foams produced showed excellent tear resistance and were near white in color.
In the above described foams, difficulty is encountered in both the processability and in the control of cell size and cell distribution. It is desirable to have a highly processable foam with small, uniform cell sizes and distribution while retaining adequate resilient foam properties.